Sound doesnt match video???

I have tried playing movie files from my laptop (mainly AVI and MPEG)on to my TV using S-Video. The picture comes up fine....but the sound does not match the peoples lip movements on screen.
It seems to be a few seconds delayed. Sound hookup I am using is 2 RCA plugs (white and red) into my amp, and then into my laptop headphone port.

Can anyone please help me and tell me how to get the sound matching the picture??

A fragmented drive can affect hard drive performance too....... Mismatched video and sound is a driver or codec problem! I had the same problem when I first got my LCD monitor! I connected the secondary s-video (on my video card) to the HD tv and when I tried playing anything, the sound was off about a second or so! I searched for updated codecs and video drivers, looked for any settings for tv monitor and played with them! Its been a while so dont remember exactly what I did..... but try all of these? Also what video card do you have? How fast is ur processor and how much mem do you have?